As an apparatus for forming a thin film, e.g., a silicon oxide (SiO2) film or the like, on a semiconductor wafer (hereinafter referred to as “wafer”), there is known, e.g., a semi-batch-type apparatus. More specifically, a rotary table configured to rotate about a vertical axis within a vacuum container is installed in the apparatus. On the rotary table, recess portions as slots for receiving wafers are formed at a plurality of locations, e.g., five locations, along a circumferential direction.
In between the vacuum container and a load port on which a wafer transfer container (a FOUP: Front-Opening Unified Pod) is placed, a transfer module, a load lock chamber and a loader module are arranged in the named order from the side of the vacuum container. For example, five wafers existing within the FOUP are moved into the vacuum container one after another using transfer arms respectively arranged in the transfer module and the loader module, while intermittently rotating the rotary table. Thereafter, the respective wafers are revolved by the rotary table and a process gas is supplied to the respective wafers, thereby forming thin films on the wafers with increased uniformity.
In this film forming apparatus, there is a demand for evaluation of the properties of a thin film formed in one of the five slots. Although thin films having the same properties are obtained in any of the slots as mentioned above, it is sometimes the case that the reproducibility of the thin film properties is checked with respect to a specific slot. In this case, if film forming processes are equally performed in the remaining four slots other than said one slot, costs are increased just as much as the number of the wafers placed in the remaining four slots. On the other hand, if a film forming process is performed by placing a wafer only in said one slot without placing wafers in the remaining slots, thin films are formed on the bottom surfaces of the remaining slots. This may become a cause of contaminating the rear surfaces of other wafers in a subsequent process or generating particles. In the related art, there is no description on the technology for evaluating the properties of a thin film formed in a specific slot.